Offline Chemical Characterization And Source Analysis Of PM_2.5 In Urban Area Of Yangtze River

Detailed chemical characterization of fine aerosols (PM2.5) is important for reducing air pollution in densely populated areas, such as the Yangtze River Delta region in China.This study systematically analyzed PM2.5 samples collected during November 2015 to April 2016 in urban Yangzhou using a suite of techniques, in particular, an Aerodyne soot particle aerosol mass spectrometry (SP-AMS). The source analysis for the inorganic components and organic components respectively, followed by trajectory analysis of a region of atmospheric aerosol delivery source. The above analysis gives the following conclusions:1. All quantitative components, including OM, EC, inorganic components and trace metal elements, are capable of reconstructing PM2.5 with an average of 91.8% quality.NH4NO3, (NH4)2SO4, and NH4Cl are inorganic components that are mainly included in PM2.5. Organic matter (OM) consists of 65.4% secondary organic (SOM) and 34.6% primary organic (POM). The results showed that water-soluble organic matter(WSOM) accounted for 60.3% of total OM.2. Source analyses of inorganic components showed that secondary nitrate, sulfate and chloride were the major species, while primary sources including biomass burning,coal combustion, traffic, industry and re-suspended dust due to nearby demolition activities, which could contribute to other species.3. Correlation analyses suggested that WSOM might be rich in secondary organic species, while WIOM was likely mainly comprised of primary organic species. We further conducted positive matrix factorization (PMF) analyses on the WSOM, and identified three primary factors including traffic, cooking and biomass burning, and two secondary factors. We found the secondary factors dominated WSOM mass(68.1%), and their mass contributions increased with the increase of WSOM concentrations. Relatively small contribution of primary sources toWSOM was probably due to their low water solubility, which should be investigated further in future.4. The results of the backward trajectory show that Yang Zhou PM2.5 pollution is seriously affected by regional emissions, rather than long-distance transmission of aerosols and its primary pollutant emissions are more important for local PM2.5 contributions.Overall, our findings improve understanding of the complex aerosol sources and chemistry in this region.